Hi there. Thanks for all the great info. I'm considering adding a second bathroom to my slab home in Florida. This will be on the complete opposite side of the existing bathroom, so tying into anything existing is not feasible (except water which I can pull from the garage).

What I want to do is bring a new four inch line straight in from my yard (the main) directly to a toilet flange, then continue that line (reduce to two inch) up as a new vent stack. Then drain my sink and tub into the 4 inch line (this would require the toilet flushing past wherever I tee in into the 4inch line) then tie the sink and tub vents into the vent stack.

Would the tub and sink be vented this way? I know code says can't have a major draining past an unvented minor, so would this be considered vented? I don't know if this would work. Is there an easier/simpler way to do it? (My problem is that there will be a doorway between the sink and the toilet/tub, so I couldn't just drain the sink into the vent stack)

Thanks for the great advice!

Hey Migualito, greetings from Sarasota,

You are correct. You can not discharge a major fixture past unvented minor ones. If I understand you would be flushing a vented toilet past a lav and tub which are then revented back into the toilet vent. I guess that would would work but you asked for a easier, simpler way. First off forget the toilet and the tub vent. See, it's getting simpler already.
Most bathroom groups are roughed in like this.
Toilet connects to sewer main. The toilet wet vents through the lavatory vent. Lavatory connects to toilet drain and runs a vent out the roof or revents back into a dry vent in the attic off the top the stubout tee. The shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes but also The Standard Plumbing Code Book.
Sound like a plan? Good luck, Tom

Thanks for the reply! The one thing I don't get is if the shower drains into the lavatory, wouldn't that be a 2 inch drain into a 1 1/2 inch? Thanks again!

No, The lavatory's picked up by a 2 X2 X 1 1/2" sanitary tee. The lavatory drain line and vent will be 2". Regards, Tom

This site is awesome... but I am still having some problems w/my layout... I don't think that the way we discussed above would work w/ my layout...

The main line will come in straight from the backyard, pretty much in line with the toilet, so sitting on the toilet, the drain line will be laying underneath in front of you. Also sitting on the toilet, the tub will be on your left. When sitting on the toilet, the vanity will be in front of you, to the right. (will be a seperator wall w/ pocket door)

So here is what I was thinking... Wye off the main line before the toilet picking up the tub and vent. Another Wye closer to the backyard picking up the sink and venting up connecting to the other vent in the attic.

Now that I'm thinking about it, how would I pick up the vent and tub drain off this wye near the toilet... hmm... so confused... anyhow, how would you vent drain this set up, if you can picture it!

Also, when roughing in water lines, what is the order followed? First tub, toilet, etc? Thanks so much for this site's service!

It would have sure helped to know which way the slope of the job ran.when I
Laid it out on paper. But you asked about the tub vent and I don't need to know the pitch to answer that.
Wye off the main to the tub. Another wye on the tub drain line ROLLED UP ON A 45 DEGREE ANGLE downstream from the trap to run back to the wall and up for a vent to be revented back to the lavatory vent. The reason for the 45 degree roll up is that, unlike the lavatory vent, the tub vent will not be washed by a fixture. It will be a dry vent. If it were flat discharge and build up from the tubs waste could enter the wye. Normally this would be washed by a fixture and cleaned out but being a dry vent we roll it up so nothing will enter the wye to clog it. I hope I've explained it to your satifaction and not added to the confusion.
Typically, the bathroom branch is 1/2" off a 3/4" main with the lines run the easiest way but if I have a choice I run a dedicated 1/2" line to the toilet. Then if the toilet's flushed with someone in the shower they won't get parboiled.
Regards, Tom

Thanks! I understand perfectly, except for the roll up on the wye for the tub. (a 2" wye right?) So in essence, the main comes in, wye for the sink, wye for the tub, and then continues to the toilet.

Then on the line that goes to the tub, another wye to run the vent up the wall. This wye should be angled so that is not laying flat is what I'm understanding?

Then the two vents, (the sink and tub one) would connect up tope in the attic. Does this sound right?

Thanks again!

" i understand perfectly, except for the roll up on the wye for the tub."
I can't explain it any plainer then this," 4 X 2" Wye off the main to the tub. Another 2" wye on the tub drain line ROLLED UP ON A 45 DEGREE ANGLE downstream from the trap to run back to the wall and up for a vent to be revented back to the lavatory vent. The reason for the 45 degree roll up is that, unlike the lavatory vent, the tub vent will not be washed by a fixture. It will be a dry vent. If it were flat discharge and build up from the tubs waste could enter the wye. Normally this would be washed by a fixture and cleaned out but being a dry vent we roll it up so nothing will enter the wye to clog it."

"Then on the line that goes to the tub, another wye to run the vent up the wall. This wye should be angled so that is not laying flat is what i'm understanding? "
You got it!

"then the two vents, (the sink and tub one) would connect up tope in the attic. does this sound right?"
The lav and tub vent can be tied together and then revented back to a existing roof vent if you wish. Bear in mind that when you revent back to a single roof vent and if you wish to snake out the lav or tub vent you will have to cut it loose and snake from the attic and then reconnect it. Regards, Tom